1. Field of the Invention
The invention generally relates to protected power conversion apparatus and is more particularly concerned with compact and inexpensive power conversion apparatus for employing the single-phase and direct current outputs of conventional airborne power supply to generate stable, regulated three-phase power signals on wye-connected grounded neutral, distribution lines.
2. Description of the Prior Art
Generally, airborne power supplies for aircraft navigation instrumentation and control systems have fallen mainly into two categories. For example, a first kind of voltage regulated supply furnishes only limited amplitude single-phase power, no three-phase power being generated. Relatively high levels of direct current power, such as at 28 volts, are also provided. For direct use in aircraft so equipped, instruments and controls for the aircraft are designed primarily for the use of direct current and secondarily for operation with single-phase alternating current.
On the other hand, many types of aircraft instruments and controls are purposely designed to operate primarily from a second class of power supply providing a relatively high power, three-phase output. Such supplies normally provide regulated 115 and 200 volt levels of alternating current on four-wire, grounded neutral, power distribution lines. A secondary provision of relatively lower power level direct current at, say, 28 volts, is also often made by the second class of power supply.
It is often desired to operate equipment designed for use with one such class of power supply with the other class of power supply, a situation requiring interconnecting power adaption or converting elements. In particular, the present invention is concerned with the operation of apparatus originally designed to operate with the foregoing second class of power supply and with converter means enabling it to operate safely and efficiently with the first class of power supply. For this purpose, inverters yielding three-phase energy have been employed in the past with some success; however, such inverters are expensive and heavy and excessively consume valuable space within the aircraft fuelage. Because of these and other disadvantageous factors, inverter systems do not represent an attractive solution to the problem.